1. Field of the Invention
The present invention relates to an optical element, such as a circular polarization controlling element, for use in a display element such as a liquid crystal display element or an organic electroluminescent display element. More particularly, the present invention relates to: a retardation element comprising a liquid crystal layer made from a polymerizable liquid crystalline material; a display element comprising the retardation element; and a process of producing the retardation element.
2. Description of Related Art
Retardation films (retardation elements) comprising liquid crystal layers made from polymerizable liquid crystalline materials are known as optical elements for use in display elements such as liquid crystal display elements and organic electroluminescent display elements, and are widely used as components (λ/4 retardation films and λ/2 retardation films) of absorption circular polarizers that constitute display elements. These retardation films are also used for linear polarizers and for viewing angle compensators of a variety of liquid crystal modes.
Such a retardation film is usually prepared by stretching a polymeric film in a definite direction, and its retardation value is made uniform over the film plane. Japanese Laid-Open Patent Publication No. 54212/1997 proposes, in connection with the structure of a liquid crystal display element, a retardation film whose pixel-corresponding area and non-pixel-corresponding area have different retardation values.
The above-described conventional retardation film, however, has a retardation value that is constant in one pixel even if a display element into which the retardation film is incorporated is a color display element. Therefore, in the case where the display element is a color display element (in the case where the display element has pixels, each pixel being a triad of red, green and blue display sections), red, green and blue light that pass through the display sections of the pixels in the three colors are polarized into different states because of their wave ranges. Namely, as shown in FIG. 10, in the case where a combination of a retardation film 10′ having a retardation value of λ/4 for light that is roughly in the green wave range and a linear polarizer 20 is used as a circular polarizer, unpolarized light that has entered the circular polarizer from the linear polarizer 20 side becomes linearly polarized light as it passes through the linear polarizer 20, and this linearly polarized light becomes circularly polarized light as it passes through the retardation film 10′. However, the degree to which linearly polarized light is converted into circularly polarized light by the retardation film 10′ varies depending upon the wave range of the linearly polarized light, so that the state of polarization of the circularly polarized light finally obtained is inevitably varied.